Dr. David King, a trauma surgeon at Massachusetts General Hospital, remembers the Boston Marathon bombings quite well.
"We tried to let only the patients who were really dying into the ER," he said.
King spoke to students about his experiences at the marathon Friday at Mount St. Charles Academy, his alma mater.
He wasn't supposed to work that day. But after running the marathon, he ran to the hospital to help.
"We challenge our students to use their gifts to serve others. We think Dr. King is a perfect example of what it is we ask our students to be and to do," said Herve Richer, president of Mount St. Charles.
Richer taught King as a seventh-grader. The school invited him back hoping he'd inspire young students to do big things.
"The events and response is actually an inspiring story, and that's what I hope to give them -- some inspiration, maybe that they'll take with them a little while, perhaps for a lifetime," King said.
King also served as a trauma surgeon in Afghanistan.
He said that training and the marathon mentality helped him power through to help run the ER after pushing through 26.2 miles.
King told students they have two jobs in life -- to inspire and be inspired.
"The little events that you do, you have no idea how those are going to affect people, 10, 20, 30 years down the road," he said.